The construction depicted in the introduction is very common, particularly in paper machines, especially between the press section and the drying section of the paper machine. In this position, it is usual to lead the web threading tail in a specific way. In practice, in the beginning of the tail threading, the web threading tail is led in a known way from the press section on the surface of the fabric to the first drying cylinder and from there down to a pulper. Once the movement of the web threading tail has settled, the web threading tail is transferred in the cross direction of the paper machine to the web threading device of the drying section, which takes the web threading tail through the drying section. The two-stage operation is used in an attempt to avoid web breaks in the press section caused by tail threading, in which press section the tail threading is laborious.
At its simplest, an operator detaches the web threading tail from the surface of the fabric and transfers it laterally by hand, so that the web threading tail, which is moving forward the whole time, travels on to the next web threading device. Generally, the web threading device in question is a totality formed of ropeways, with the web threading tail being transferred to the rope throat that this forms. Usually, at least one ropeway is between the fabric and the operator, so that the operator's hand is always in danger of striking the rope of the ropeway. The situation is further aggravated by the cramped space and poor visibility. Additional major safety risks are the large rotating machine parts, the rapidly moving fabric, and especially the ropeways.
In order to avoid manual transfer, devices have been developed that would allow the web threading tail to be transferred laterally. One such device is disclosed in U.S. Pat. No. 4,542,160, in which two blower elements are used in combination. An improvement of the said device is disclosed in U.S. Pat. No. 4,784,443. In both applications, the first blower element is used to detach the web threading tail from the surface of the fabric. Similarly, the second blower element is used to create a blast essentially in the cross direction of the paper machine, and which is used to move the web threading tail laterally. However, the blower elements are at least partly in the area of travel of the web and are thus liable to be broken. In addition, they collect loose material on top of themselves. Further, the blasts are also difficult to control and their operation is otherwise imprecise. In other words, the use of blasts to transfer the web threading tail is imprecise and uncertain. In addition, the blasts are only suitable for pulp webs with a low grammage.